Selective relay



Jan. 31, 1939. c WALLACE 2,145,821

SELECTI VE RELAY Filed June 1, 1936 3 Sheets-Sheet 1 1 N VEN TOR.

cw Emma.

5 KWMM Jul. A TTORNEYS Jan. 31, 1939.

c. FQWALLACE 2,145,821

SELECTIVE RELAY Filed June,1, 1936 3 Sheets-Sheet 2 IN VEN TOR.

M A TTORNEYS.

Jan. 31, 1939. Q R WALLACE 2,145,821

SELECTIVE RELAY Filed June 1, 1936 3 Sheets-Sheet 3 (5' INVENTOR.

3 BY q 4 011-7114, KM

Z; ATTORNEY:

Patented Jan. 31, 1939 PATENT OFFICE SELECTIVE RELAY Charles F.

Wallace Wallace, Westfleld, N. 1., assignor to & Tier-nan Products, Inc.,

Belleville,

N. J.. a corporation of New Jersey Application June 1, 1936, Serial No. 82,724. In

Canada June 4, 1935.

18 Claims.

This invention relates to selective relays and more particularly to relays or kindred translat ing devices which are adapted for selective response to currents having a predetermined'frequency or periodicity.

One of the principal objects of the invention is to provide improved relay apparatus of the character described, which is mechanically tuned for the desired selective response and which is sensitive, accurate and adapted to consume relatively little power for its operation.

Another object is to provide new mechanically tuned relay apparatus which can be very sharply tuned, although capable of adjustment or'variation in size or proportions so as to be tuned for response to any of a wide range of frequencies (notablyincluding relatively low frequencies) and which is adapted to maintain its tuning at the predetermined frequency, without being appreciably affected by ambient temperature, humidity, or the like.

Further objects are to provide novel means of the character described which will respond to an alternating current having a predetermined frequency or to a pulsating or periodic direct current having a corresponding predetermined frequency or rate of pulsation; and to provide such apparatus which includes new and efllcient instrumentalities or combinations thereof for effecting a continuous or sustained circuit-controlling operation upon response to either type of current; and also to provide new and effective arrangements whereby a continuous or sustained circuit-controlling operation may be performed in selective response to an energizing current having a very low frequency or rate of alternation or pulsation, of the order, say, of five cycles per second.

Still further objects include the provision of relay apparatus of the character described which is relatively simple in operation, having relatively few moving parts, and which is economical to build and operate, and which needs little, if any, attention or adjustment over long periods of time; and the provision of improved selective relay devices and associated instrumentalities which are suitable for effecting automatic response to a calling signal in a. receiving station of a signalling system,-for example, as in radio telephone systems where it is desired to operate a call bell only upon reception of a carrier having a predetermined modulation frequency, or for corresponding operation of electrically controlled apparatus in response to a similar signal, as in systems for remote control by radio.

In Great Britain June 4,

Other objects and advantages will appear as the invention is hereinafter disclosed.

Referring to the drawings, which illustrate what are now considered to be advantageous physical embodiments of the invention:

Figure 1 is an elevation, with one end plate and a part of the other end plate in section, of one type of relay apparatus.

Figure 2 is a horizontal section on line 2-2 of Figure l, with certain parts' shown broken away or in dot and dash lines.

Figure 3 is a side elevation, with certain parts in section on line 33 of Figure 2, and other parts removed or shown broken away, of the apparatus shown in Figures 1 and 2.

Figure 4 is a detail elevation, corresponding to a portion of the elevation shown in Figure 3, of a modified form of part of the apparatus.

Figure 5 is a wiring diagram of the apparatus shown in Figure 1.

Figure 6 is a perspective view of certain parts shown in Figure 1.

Figure 7 is a perspective view of the working parts of a supplementary relay device included in the apparatus shown in Figure 1.

Figures 8, 9 and 10 respectively represent,'in plan view, different stages in the operation of a modified form of contact operating arrangement adapted for embodiment in apparatus of the type shown in Figure 6.

Figure 11 is a detail section on line of Figure 9.

Referring particularly to Figures 1, 2, 3 and 6, the relay apparatus includes a stationary electromagnetic field or stator and an armature or rotor. The field comprises the two coils or electromagnets 20, 2| each of which consists of a coil of wire, of suitable size and number of turns depending on the impedance which it is desired to introduce into the energizing circuit of the relay apparatus for most sensitive response at the predetermined frequency; each of the coils 20, 2| being wound on a frame or spool 22 of appropriate insulating material such as Bakelite. The two coils 20, 2| thus respectively constitute two sections of an air core solenoid, connected in series so as to comprise in electrical and magnetic effect, a single solenoid. The coil sections 20 and 2| are suitably mounted on posts 23 which are conveniently integral extensions of a base plate 24. A vertical shaft 25, passing between the coil sections 20 and 2 I, is journalled for oscillation in suitable bearings at each end, viz., bearing 26 in the base plate 24 and bearing 21 in an end plate 28 which is in turn secured to a pair of upright posts 29, 29,

ing and they are appropriately axially adjustable.

As particularly shown in Figure 3, each of these bearings thus comprises a plurality of balls, in

,the present case three, between which a conical end of the shaft 25 seats. Each of the bearings is externally screw threaded so as tobe capable of being advanced into or withdrawn out of the cor responding base or end plate 24, 28, lock nuts 30, 3| being respectively provided to secure the bearings in the desired relative position of axial adjustment.

Secured to the shaft 25, as by means of the bushing 32 (including a collar and set screw for adjustability), is the armature or rotor 33, which preferably comprises a permanent magnet, i. e., permanently magnetized or poled so as to have a north pole at one end and a south pole at the other; such permanently magnetized armature is advantageously constructed of metal of the nature of cobalt steel. It will be appreciated that by virtue of the manner in which the armature is mounted on the shaft 25, and in which the latter is journalled in the end plates, the armature 33 may be accurately positioned with respect to the field or stator, and will oscillate freelyabout the axis of the shaft, with comparatively llttl'eiriction at the bearings, and without undesired radial or end-play of the shaft.

Also secured to the shaft as by a collar and set screw 34, is a torsion spring 35 which convenient-e 1y extends helically around the shaft andt'isse-j v Celluloid-1Alternatively,.the shoe 42 may bemade of suitable wear-resistant insulating material and cured at its other end 'to the stationary framework, as by frictional engagement'with a helical groove in the outer surface of the lock nut 30;

The helical torsion spring 35 is thus-secured to j;

the shaft so as to oppose'deflection of the armature 33 from its normal position, and to exercise force to restore it to normal position when ,it is deflected therefrom by the passage of suitable current through the solenoid 20, 2|. The weight of the shaft 25 and its appended parts,'particularly including the armature 33, together with the tension of the spring 35, are so fashioned'or adjusted that. the assembly carried by and including the shaft 25 constitutes a torsional pendulum having a natural period of mechanical resonance or oscillation equal to thecurrent frequency or periodicityto which the relay is intendedto re-' I spend. 1

A-set of contacts, to be operated upon appropriate rotation or oscillation of a cam 36, carried by the shaft25 are provided, as particularly shown. in Figures 1, 2, 3 and 6. This contact set comprises a spring strip 40 carried at one end by a stud 4], but suitably insulated therefrom (see particularly Figure 2) and provided at its free end with a wear-resistant metallic shoe 42 for engaging the cam 36. The spring strip 40 is provided also with a contact 43, preferably convstructed 'of one of the rare metals commonly employed forelectrical contacts. By virtue of the inherent resiliency of the strip'4|l,'contact 43 is biased toward and adapted to engagea similar contact 44, secured to a metallic strip'45 carried by, but'insulated from, the stud 4| 'the' strip 45 being backed up or reinforced by 'a cornparatively heavy metallic strip 46, provided with an adjusting screw 41. The strip 46 is also car -,ried' by, but insulated from, the stud 4|..'

turning the screw 41, in one direction orthe' other, the gap or distance between the contacts 43, 44 may be adjusted as desired. 'The stud 4| in Figures 1 a nplemen a.

, is secured to a pivot block 48=adapted to oscil- .late aboutthe' standard or post 23, uponwhich it is mounted. A helical spring 49 has one of its ends secured to; the post and its other end 'se-I cured to the-pivot block'48 whereby'the contact assembly is biased or urged by the spring 49 in a counterclockwise direction (Figure 2); the'extent of such movement being limited by the engagement of a stop pin 50'secured to the pivotblockffl and after performance of any of jsuch op'erations f as may. .be ,necessarypndesired, the spring: 49,.

automatically returns the contact set to itsope'raor th St p s- 5 s a It maymen t' dtth tthe base member- 24, m

tive' position'as determined by the engagement the supporting posts 23, 2 3 and 29, 29,- are preferably-made of metal-inane piece,as bya die cast-,1 ing. The end plate-'28, also conveniently made of metal,.can beinsulatedfrom its supporting posts 29, "29yas by inSulatingfWashers-SZ (seeFiguresl and 3)], so as to obviatelosses which might arise 1 if; theiram'e, constituted, electrically,- a closed @loop.1

I The'wear-resisting. metallic shoe 42 of the tact assembly is engaged andmechanically opera ated 'by'th'ef cam 36, which is constructed of suit-" able'wear-resistingmaterial such as ebonite or the cam 36 made of wear'resistantmetal. v

N In the'apparatus here shown, the arrangement of the contact assembly and cam .35 is such that: when-jthefcoils 20, 2| are. not energized at the .=predeterminedfrequency, the armature is maintainedin its normal'orfrest" position byfthe spring 35 f(.th'ef'.magnetic axis of the armature 33.

nd,3, to the magnetic axis of the nveniently at right anglesjas shown 2|) 'and thecontacts 43, 44, are open." th'thearmature in such'positiomthe of engagemnt withithe shoe 42, so that contact] contatM JqA studor stop 54, extending down from the ndjplat'e"28, intercepts the path of the 43 coineslinto: circuit-closing engagement with armature} 33, convenientlyat a-point directly opp'osit'e one side o'f'the solenoid 20, 2| (see Figures 2-ana-,s =so s to limit the extentfof deflection of the armature 33in eitherdirection,

mentary may, generally designated .60, can be,

if desired, ,mountd; on the opposite face of the' base plate 24" from the apparatus just described, v and gmay comprise, for example; any efilcient standard type of. relay; suitable for effecting the desired circuit, control. Preferably;although not essentially in all case's, this relay is non-chatter- For.ordinaryoperatlon of the apparatusito, efie'ct' continuous j circuit-cont'rolling operatic ns,v

relays-is provided. This supple- I ratus may also carry,

same or a difl'erent type of relay may be employed to open normally closed contacts, or to perform any number of those or any other kinds of circuitcontrolling operation. Referring more particularly to Figure 7, which shows the working parts of the relay 60, the latter is seen to include a solenoid and core 6|, having an L-shaped armature 62, of which one arm 63 has secured thereto a rigid operating strip 64 passing through an aperture 65 in an upright member 66 secured to the end of the solenoid core 6|, upon which end the armature is fulcrumed. This upright member 66 may conveniently form a part of a bracket 61 which serves tomount the relay 60 upon the base plate 24 (see Figures 1 and 3). Instead of the edge of the core 6|, the adjacent configuration of the bracket 61 may be such as to provide a fulcrum for the armature 62, i. e., so that in either case the armature is in effect pivoted at its end opposite the end 68, for movement downwardly (in Fig. 7) upon energization of the solenoid 6| (attracting portions 68 and 63 of the armature). A pin 68a, extending, as shown, through the armature part 63 and a part of that end oi core 6| to which member 66 is fastened, loosely secures the armature to the solenoid for preventing lateral displacement of the armature while permitting it to rock downwardly (and back upwardly) as just explained,

The outer end of the rigid strip 64 conveniently engages the upper edge 63 of an aperture in a vertical extending link 10, which is urged or biased downwardly by the tension of a spring 1|, so as to maintain the end 68 of the armature in a. position, for example, as shown, spaced from that which it would occupy upon energization of the magnet 6|. The upper extremity of the link 10 is operatively connected with an operating member of a contact device, so that when the magnet 6| is de-energized, and the link 10 is in a lower position under the tension of spring 1|, the contacts 12, 13 are opened, but on energization of the magnet 6| and consequent displacement of the armature 63 downwardly (in opposition to the tension of spring 1|), the link 10 is correspondingly moved up by the strip 64, and the contacts 12, 13 are closed. Any suitable contact arrangement may be employed; one advantageous type consists of a pair of contacts 12, 13, normally biased for closure by the spring 14, and adapted to be maintained open by engagement of one end of an operating member or lever 15 with the under side of contact 12. Thus when link 1|) is in its lower position, arm or lever 15 is so positioned relative to its fulcrum 16 as to keep the contacts open; upward displacement of link 10 frees the lever 15, permitting the contacts to close. The contact assembly just described may be conveniently mounted in a sealed glass tube, as shown in Figures 1 and 3, into which the arm 15 extends through a sealed flexible connection permitting the necessary movement of the arm. The interior of the glass tube may contain such vacuum or inert gas as will prevent arcing upon even a very slight opening of the contacts 12 and 13.

Conveniently mounted within the frame of the apparatus, as shown in Figures 1, 2 and 3, are a condenser 86 and a resistor 8|, connected as will now be described. The base plate 24 of the appainsulated therefrom (see Fig. 1), such binding posts or terminals 82 as are desired for connection of the apparatus in use.

Referring particularly to Figure 5, which shows a preferred wiring diagram of the apparatus heretofore described, it will be seen that the input 83, 84 01' the relay, viz., the circuit from which the predetermined alternating or pulsating current is to be derived for energization, is connected to the solenoid or field comprising coils 20, 2|. Contacts 43, 44 are so connected that upon closure they establish the following circuit to energize relay 66: From one side of a source of current, such as a battery suitable for energization of relay 68, through conductor 85, contacts 43, 44, resistor 8|, winding 6| a 01' the relay 68 and conductor 86, back to the other side of the battery. Condenser 80 is advantageously connected in parallel with the winding 6|a of the relay 60, as shown. Contacts 12 and 13 are connected, as will now be understood, in the circuit to be controlled upon the desired selective response of the relay apparatus. It will be appreciated that by virtue of the discharge of the condenser 88, relay 60 will be maintained energized, and its contacts 12, 13 consequently closed, for an appreciable length of time after an opening of contacts 43, 44, and even though these contact may only be closed momentarily. The resistance 8| serves to prevent surges of current, e. g., into the condenser 80, such as would cause harmful arcing across contacts 43, 44 when they are opened and closed in rapid succession, i, e., so as to prevent pitting or like injury to these contacts.

It may now be explained that when a. periodic current, such as an alternating current, or a periodically varying current, or a periodically pulsating current, or a periodically interrupted current is impressed on the input circuit 83, 84, and its periodicity is that of the natural mechanical periodicity of the shaft 25 and assemblage carried thereby, the armature 33 will be swung insynchronism with the current variations (i. e., the current variations traversing the solenoid 20, 2| through which the armature 33 is adapted to swing) and will reach an amplitude of oscillation suificient to rotate the high point of cam 36 well away from the shoe 42 and permit a consequent closure of contacts 43, 44. Thereafter the contacts 43, 44 close upon each such swing or deflection of the rotor 33, in either direction; each such closure of the contacts 43, 44 energizes the relay 6|] and charges the condenser 80, and the discharge of the condenser 80 maintains the relay 60 energized upon subsequent temporary opening of the contacts 43, 44 (while the rotor 33 is passing through the central part of its swing from one position to the other). In this manner the contacts 12, 13 are closed and maintained closed by the efiect of current, having the proper predetermined periodicity, flowing through the coil sections 20 and 2|. Current of a different periodicity through the coil sections 20, 2| will not, however, produce such response because the electromagnetic torque impulses exerted upon the armature 33 will not be in synchronism with the mechanically tuned assemblage including the shaft 25 and the structure carried thereby.

The periodicity of the torsional pendulum comprising the assemblage 25, 33, and associated parts is determined generally by suitable relative design of the parts. A finer desired adjustment may be obtained, for example, by adjusting the effective length of the helical spring 35. Such last mentioned adjustment may be conveniently made by rotating the lower end of the spring in its groove in the nut 30, and by correspondingly rotating the collar 34 (after loosening the set screw thereof) about the shaft 25 so as to maintain the armature 33 in its desired position of rest.

In some cases, as where the relay apparatus is so designed or is so located with respect to other apparatus that eddy currents (set up about the solenoid, 20, 2I and in adjacent metallic parts of the relay or other apparatus) might have some detrimental eflect, suitable flux-localizing means may be employed, such as additional soft iron armatures carried by the shalt above and below the solenoid 20, 2I. Another arrangement for increasing the sensitivity and reliability of the relay in such cases, is shown in Figure Here, in addition to the armature 33 normally lying within the core of the solenoid 20, 2I, the shaft 25 carries an additional permanently magnetized armature 93. This permanent magnet 93, which may be in all respects like the permanent magnet (rotor) 33, is conveniently secured to the bushing 32 so as to be in axial and radial alignment with the rotor 33. The S-pole of the magnet 93 lies adjacent the N-pole of the rotor 33 and the N-pole of the magnet 93 lies adjacent the S-pole of the rotor; the poles being at the ends of the magnet 93 and the rotor 33. The permanent magnets 33, 93, located one within and one outside the coils 20, 2I, constitute an astatically balanced system.

Among others, advantages inherent in structures of this character are the minimization of eddy current losses, and at least to a certain extent, the provision, by each magnet, of a keeper for the other, so that the magnetism of each is the more permanently maintained. Furthermore, the magnet 93 may constitute in efiect a supplemental rotor, and may serve, where desired, to increase the moment of inertia of the torsional pendulum about the axis of shaft 25. Astatically balanced or other flux-localizing arrangements of the types described serve also to prevent deleterious effects due to any nearby iron parts or electromagnetic devices, e. g., such parts or devices as may be present in other relays or like apparatus located near the relay apparatus.

The arrangement shown in Figures 8 to 11 includes certain modifications useful in some instances, particularly with respect to the contact assembly operated by the torsional pendulum. In the modification here shown, the shaft 25 carries a contact operating arm I00, for operating and closing contacts I43 and I44 (otherwise connected and corresponding to contacts 43, 44 of the device previously described), as follows: The electrical contacts I43, I44, suitably insulated from each other, are supported by a stationary bracket I48, which may be conveniently carried by a supporting post, such as one of the posts 23, in lieu of the block 40. The contact arm I43 has pivotally mounted thereon a cam segment I49 which is biased by a spring I50 towards the stop pin I5I. When the arm I00 is defiected from its normal position to a sufllcient extent it flips idly by the contacts by virtue of the fact that when the end of the arm I00 engages the segmental cam I49, the latter swings away from its back stop without operating thecontact arm I43 to close the contacts, as shown in Figure 8. But on the return stroke, 1. e., to-

ward normal position, the same end of the arm I00 engages the cam segment I49 (note the so-,

advanced position of the end of arm- I00. as indicated by dotted lines I00a in Figure 9) and causes the contact arm I43 to be moved toward the other contact arm I44 so as to close the 'contacts (see Figure 10) and so as to-permit the ature, humidity or the like.

arm to'pass. The contact arms I43 and I44 are normally separated by virtue of their inherent resiliency.

It will be appreciated that with the arrangement just described, oscillatory movement of the shaft 25 upon energization of the relay apparatus at the predetermined frequency to which it is to respond selectively, will cause closure of contacts I43, I44 with a corresponding periodicity and with very little frictional loss; but with the construction shown, there is only one contact closure for each complete swing of the torsional pendulum assemblage-that is, only upon deflection in one direction-in contradistinction to the arrangement shown in Figures 1, 2, 3 and 6, wherein the contacts are closed upon the arrival of the armature at each end of its swing. In order to provide two contact closures per complete oscillation, as in the previously described arrangement, an additional contact assembly similar to that shown in Figures 8 to 11 inclusive, may be mounted. upon another supporting post in such position as to be operated by the opposite end of arm I00 when the latter is swung in an opposite direction to that which effects operation of contacts I43, I44. Such additional contacts, it will now be understood, can be conveniently connected in parallel with contacts I43. I44.

If desired, the shaft 25 may carry such an arm I00, either to operate a contact assembly as shown in Figures 9 to 11 inclusive, or merely to swing free, which carries, as shown in Figures 8 to 9 inclusive, a pair of weights I52, I52. The weights I52, I52 are respectively screw-threaded upon the ends of thearms I00, so that they may be individually and accurately moved toward or away from the shaft 25. Means are thus provided for effecting a delicate adjustment of the balance of the torsional pendulum assembly and also for providing a further adjustment of the periodicity of that assemblage, as by moving both weights I52 toward or away from the shaft to increase or decrease the natural frequency of oscillation of the assemblage.

One form of my invention, including the instrumentalities shown in Figures 8 to 11 inclusive, is disclosed but not claimed per se, in the copending applications of John R. MacKay,

Serial Nos. 730,127 and 11,783, respectively filed the base plate 24 in Figure 1 and may have its open edge fastened down to abut against the shoulders I54, I54 on the base plate.

It will now be appreciated that apparatus of the type described affords a particularly sensitive and eilicient selective relay, which is sharply tuned for response only to the desired alternating, pulsating, varying or interrupted cur- 'rent.- The mechanical tuning arrangements provide means for maintaining the relay at its desired tuning or resonance irrespective of electrical circuits or conditions and without appreciableefiect due to variations in voltage, temper- The apparatus is simple in operation, sturdy, and easy of access for inspection, cleaning, repair or adjustment; its

operation involves remarkably little loss due to friction. At the same time, the arrangement of the energizing solenoid 20, 2|, and the torsional pendulum including the magnetized armature 33, is such as to provide a sustained and vigorous action (with relatively heavy contacting pressure, as at contacts 43, 44) upon application of the predetermined energizing current, and to prevent, particularly when the spring 35 is made relatively stiil, any minor, harmonic, or inadvertent operation under the control of currents to which the relay apparatus is not intended to respond. Furthermore, the apparatus afiords eflicient selective response at relatively low frequencies, and obviates the disadvantages in many tuned relays of the vibrating reed or tuning fork types, which are only satisfactory at such high frequencies as to cause rapid wear of their rapidly making and breaking contacts, and which are susceptible of fatigue or are characterized by large temperature coefiicients, so that they are apt to creep" or otherwise depart from the desired tuning.

It will be understood that in some cases contacts 43, 44 may be adapted to open instead of close upon deflection of the torsional pendulum assemblage, or may be adapted to perform a plurality of circuit-controlling operations. Likewise, as previously explainder, supplementary relay 60 may assume a variety of forms, so as to achieve any desired type or types of predetermined circuit-controlling operation upon energization or de-energization of the selective relay apparatus.

The arrangement shown is furthermore such that even though relatively strong currents of the wrong frequency (i. e., currents or impulses having some other periodicity than that to which the relay is intended to respond) are impressed upon the solenoid 20, 2|, the mechanical impedance, so to speak, of the armature assembly will ordinarily prevent its building up to a sufiicient amplitude of oscillation for closure of contacts 43, 44. That is, even with relatively strong current, the first deflection of the armature will be insuflicient to operate the contacts, and if the current is of the wrong periodicity, its next and succeeding impulses will be out of step with the natural period of the assembly and will thus actually oppose or prevent its oscillation. Furthermore, even if a casual deflection of the armature should, although it is unlikely, efiect a closure of contacts 43, 44, such isolated closures could not effect sustained energization of the relay 60, nor the predetermined sustained circuitcontrolling operation of contacts l2, 13.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, together with the apparatus which I now consider to represent the most advantageous embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results oultined, and the invention extends to such use within the scope of the appended claims.

I claim:

1. A selective relay device, comprising in combination, a torsional pendulum having associated therewith circuit-controlling means adapted to be operated upon'rotative oscillation of said pendulum at its natural period and adapted for free Pendulum rotation unobstructed by said means, said pendulum having torsional mounting means adapted to prevent non-rotative displacement of the pendulum, and electromagnetic means for imparting driving torque to said torsional pendulum in accordance with the periodicity of energizing current supplied to said electromagnetic means.

2. A selective relay device comprising circuitcontrolling means, an electrically independent, torsionally suspended, magnetized armature having a natural period of rotative oscillation, an air-core stator coil for imparting oscillatory driving force to said armature, said armature being disposed for rotative oscillation within said coil, and means responsive to rotative oscillation of said armature at its natural period for operating said circuit-controlling means.

3. A selective relay device comprising circuitcontrolling means, an electromagnetically driven torsional pendulum for eifecting operation of said means upon rotative oscillation of said pendulum at its natural period, said pendulum comprising a rotatable mass, means resiliently holding said mass against rotation, and journalling means supporting the weight of said mass independently of said last-mentioned means.

4. A selective relay device comprising circuitcontrolling means and an electromagnetically driven torsional pendulum for eifecting operation of said means upon rotative oscillation of said pendulum at its natural period, said pendulum including a member journalled for rotation, a spring adapted to bias said member against rotation, and adapted for adjustment of its effective length to vary the natural period of the pendulum, and means adjustably securing said spring to normally maintain said member in a predetermined position of rest upon adjustment of the effective length of the spring.

5. A selective relay device comprising a contact device, a permanently magnetized arma-' ture torsionally suspended for oscillation at a predetermined natural period and in a rotative direction only, said armature having mounting means adapted to prevent non-rotative displacement of the armature, stationary electromagnetic means comprising an open-cored solenoid for imparting oscillatory driving force to said armature, said armature being adapted to oscillate into and out of the core of said solenoid, and means responsive to oscillation of said armature at its natural period for operating said contact device.

6. A selective relay device comprising a contact device, a member of ferrous metal torsionally suspended for rotative oscillation and having mounting means for preventing non-rotative displacement of said member, stationary electromagnetic driving means for said member, and means responsive to displacement of said member for operating said contact device.

7. A selective relay device comprising a set of contacts, a tuned torsional pendulum device having a natural period of rotative oscillation, electromagnetic means for imparting oscillatory driving force to said pendulum in accordance with the periodicity of energizing current supplied to said electromagnetic means, and means mechanically responsive to oscillation of said pendulum device at its natural period for effecting the same operation of the same aforesaid set of contacts during each half cycle of oscillation of the pendulum device.

8. A selective relay device comprising stationary electromagnetic means comprising an aircore winding, circuit-controlling means, and means for operating said circuit-controlling means upon predetermined periodic energization of said electromagnetic means, said operating means including a permanent magnet yieldably supported for oscillation within said air-core winding and having a predetermined oscillatory period.

' 9. A selective relay device comprising contacts and an electromagnetically energizable pendulum mounted for rotative oscillation and having camming means adapted for unobstructed travel of the pendulum past said contacts, for operating the contacts upon oscillation of the pendulum at its natural period, said pendulum having mounting means adapted to prevent non-rotative displacement of the pendulum.

10. A selective relay device comprising circuitcontrolling means, a plurality of coil members, an electrically independent armature member which is torsionally suspended between said coil members for rotation within each of same and which has a predetermined natural period of rotative oscillation relative to said coil members and which is magnetically responsive to energization of said coil members by a current having a periodicity corresponding to said natural period, for receiving oscillatory driving torque from said coil members, and means responsive to oscillation of said armature at its natural period for operating said circuit-controlling means.

11. A selective relay device comprising circuitcontrolling means and an electromagnetically driven torsional pendulum for effecting operation of said means upon rotative oscillation of said pendulum at its natural period, said pendulum including a member journalled for rotation, a helical spring disposed coaxially with said member, means adiustably securing one end of said spring to said member for variation of the angular position of the spring relative to the member, and means adjustably securing the other end of said spring against rotation, for variation of the effective length of said spring upon rotative displacement of said other end of the spring.

12. A selective relay device adapted to perform a predetermined circuit-controlling operation upon reception of current having a predetermined periodicity, and including, in combination, a sta tionary air-core field winding and a mechanical oscillator having a natural periodof oscillation corresponding to said predetermined periodicity, said oscillator including a permanently magnetized armature mounted to oscillate within said field winding and adapted to receive oscillatory driving impulses from the field winding, and

means for effecting the predetermined circuitcontrolling operation upon oscillation of said oscillator at its natural period.

13. A selective relay device comprising in combination a shaft Journalled for rotation, yieldable means normally biasing said shaft against rotation, electromagnetic means which include an armature carried by said shaft and which are adapted, upon energization by current having a. predetermined periodicity, to effect oscillation of said shaft about its axis, said shaft, armature and yieldable means providing an assembly adapted for free oscillation at substantially only said predetermined periodicity, and circuit-controlling contact means operated upon oscillatory deflection of said shaft. I

14. A selective relay device comprising, in combination, a solenoid having an open core; torsional pendulum means adapted for free oscillation at a natural period and having a shaft adapted for oscillation about its axis, an armature mounted on said shaft for oscillation therewith into and out of the open core of the solenoid, and resilient means normally maintaining said shaft in a position of rest with the armature positioned for the exertion of electromagnetic force thereon by the solenoid to displace the armature in its path of oscillation; and contact means adapted for operation upon oscillatory displacement of said armature in response to energize.- tion of the solenoid by current having a periodicity corresponding to the aforesaid natural period.

15. A selective relay device comprising circuitcontrolling means, and electromagnetic means for operating the same upon energization by current having a predetermined periodicity, said electromagnetic means including magnetically reacting stator and armature members, said armature member being torsionally suspended for rotative oscillation relative to said stator member at a natural period corresponding to the aforesaid predetermined periodicity, and flux-localizing means magnetically adjacent to and adapted for rotative oscillation with said armature, to minimize eddy current losses upon oscillation of said armature member when the electromagnetic means is energized by the aforesaid current.

16. In a selective relay device for circuit control in response to current of predetermined periodicity, in combination, a permanently magnetized armature, mechanically tuned means whereby said armature is adapted for periodic deflection at a predetermined natural period, electromagnetic means for supplying driving impulses to said armature, and flux localizing means movable with said armature and providing therefor a magnetic path of substantially less reluctance than air.

17. The combination of claim 16 wherein said flux localizing means comprise a permanently magnetized member deflectable with said armature and astatically arranged with respect to said armature.

18. In a selective relay device for circuit control in response to current of predetermined periodicity, in combination, a solenoid, a permanently magnetized armature therefor, torsionally CHARLES F. WALLACE. 

